Start by gathering all your ingredients. Dice the onion and chop the garlic finely. You can use any type of olives you prefer, such as Kalamata or green olives, just ensure they are pitted and chopped.
In a large skillet, melt the butter along with the olive oil over medium heat. The combination of these fats will give the tilapia a wonderful flavor and help achieve a golden crust.
Once the butter is melted and bubbly, add the diced onion and sauté for about 3-4 minutes until they become translucent. Add the chopped garlic and cook for an additional minute, stirring frequently to avoid burning.
Gently place the tilapia filets in the skillet. Let them cook for about 3-4 minutes on one side, then carefully flip them using a spatula. Cook for another 3-4 minutes until the fish is cooked through and flakes easily with a fork.
Once the tilapia is cooked, sprinkle the chopped olives over the fish and let them heat through for a minute. This will enhance the flavors and allow the olives to meld with the butter and garlic.
Remove the skillet from heat and plate your tilapia filets. Spoon the olive mixture generously over the top. Serve with a side of your choice, such as steamed vegetables or a light salad, to complete your meal.